Stimulation of the elastolytic activity of leukocyte elastase by leukocyte cathepsin G

Human leukocyte cathespin G strongly stimulates the rate of solubilization of human lung elastin by human leukocyte elastase. For instance, the elastolytic activity of an equimolar mixture of elastase and cathepsin G is more than 5 times higher than that of elastase alone. Optimal stimulation occurs only if cathepsin G and elastase act simultaneously on elastin. Potentiation of leukocyte elastase digestion of lung elastin may also be brought about by bovine alpha-chymotrypsin. This enzyme is about half as efficient as cathepsin G. Stimulation of leukocyte elastase activity by cathepsin G is about 3 times less pronounced with bovine ligamentum nuchae elastin than with human lung elastin. On the other hand, the elastolytic activity of porcine pancreatic elastase is only enhanced by 20 to 30% by cathepsin. Therefore, maximal potentiation of elastolysis occurs with the lung elastin/leukocyte elastase system. The pathologic relevance of these findings is discussed.